The present invention relates to a new and improved method for underground mining, which is particularly applicable to the mining of material such as oil shale or coal, or other ore materials having about the strength of medium-strength rock.
A known method of mining coal is to utilize a machine equipped with a number of toothed wheels which are continuously rotated by a power drive, and to apply the rotating toothed edges of the wheels to the ore surface so as to progressively grind or chew away the ore material. This type of machine may be guided along a substantially horizontal path to form a drift or tunnel as the mining action progresses.
In the prior art it has also been known to apply a rotary cutting action to the end face of a bore or tunnel. Machines including a combination of cutting teeth and wedge-shaped wheels have been used for this purpose, both in mining operations and in tunnel construction.
The previously known mining techniques which have been applied in the underground mining of medium-strength materials have been subject to several disadvantages or limitations. One very serious disadvantage is that the cutting load has been unevenly distributed among the various cutting elements of the machine, causing some of the cutting elements to wear more rapidly than others. This problem has, in turn, necessitated frequent shut-downs of the machinery for the purpose of repairing or replacing the worn cutting elements.
Another serious disadvantage of the prior art methods has been that the mining action produces ore particles having highly irregular shapes and widely varying sizes. Where the ore material is refined, the non-uniformity of the particle size has added a great deal to the complexity and cost of the refining process.
Thus the principal object and purpose of the invention is to provide a method for totally mechanized underground mining, which will produce ore particles having a high degree of uniformity as to size, and which will also maximize the time between shut-downs of the machinery.
Another principal object of the invention is to provide a mining method which will remove a higher percentage of available material from the mine than has been possible with prior methods.